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Router HP Ratings?

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Forum topic by Alan S posted 08-17-2010 09:54 PM 1417 views 0 times favorited 8 replies Add to Favorites Watch
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Alan S

178 posts in 2779 days


08-17-2010 09:54 PM

Can someone explain how 110v routers are rated at 3 1/4 HP? As I understand it, 1 HP = 746 watts, which at 110v, equals about 7 amps. That would put a 3 HP motor at above 20 amps, the current ratings of just about all wall outlets. What gives? People seem to accept that for induction motors, 110v circuits can only provide 1.5 HP, anything else requires 220v. How can router manufacturers make these crazy claims about their HP?

Alan


8 replies so far

View patcollins's profile

patcollins

1420 posts in 2327 days


#1 posted 08-17-2010 11:23 PM

Because when the motor is close to stalled it draws about 20 amps

View Ingjr's profile

Ingjr

144 posts in 2478 days


#2 posted 08-17-2010 11:42 PM

Just about all the 3+HP routers I’ve seen draw 15amps at everything but start-up or stall. What’s that mean? I have no idea.

-- The older I get the faster I was.

View Ger21's profile

Ger21

1047 posts in 2593 days


#3 posted 08-18-2010 02:32 AM

Same way Sears sells 6HP Shop Vacs. Router HP is not continuous HP.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

View TopamaxSurvivor's profile

TopamaxSurvivor

17664 posts in 3138 days


#4 posted 08-18-2010 01:34 PM

I have no idea how they figure it. I saw a table saw the other day that said 3+ hp on the front. I looked a the motor and found 1 hp on the name plate but it was 3450 instead of 1725. I supposed they are using some concoction of higher rpm to claim higher hp. They probably have some shyster lawyer OKing it :-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Don Butler's profile

Don Butler

1086 posts in 2857 days


#5 posted 08-18-2010 01:47 PM

By definition of electrical horsepower, one HP equals 746 watts.

That would mean that 3.5 HP equals 2611 watts and at 120 vac that’s 21.75+ amps.

If you stall it, the load will climb up to that neighborhood, but it should also pop a 15 amp breaker.

Don

-- No trees were damaged in posting this message, but thousands of electrons were seriously inconvenienced.

View HorizontalMike's profile

HorizontalMike

7143 posts in 2376 days


#6 posted 08-18-2010 01:57 PM

The USA actually uses 120v and 240v (since ~1950s when they upped the line voltage from 110v). So with 120v x 20amps you get 2400w and end up with ~3.216hp:

http://wiki.answers.com/Q/How_do_you_convert_amps_to_horsepower

-- HorizontalMike -- "Woodpeckers understand..."

View knotscott's profile

knotscott

7210 posts in 2837 days


#7 posted 08-18-2010 02:15 PM

Their ratings are almost “mathematically” possible, but in practice they’re basically lying.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View TopamaxSurvivor's profile

TopamaxSurvivor

17664 posts in 3138 days


#8 posted 08-18-2010 07:28 PM

On small single phase motors, the reality is 1500 watts equal 1 hp. The fiine print has to be too fine to read on this one :-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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